Modern wind turbines are usually set up on beaches or on sea water for converting strong wind into electrical power. The main wearing components mounted inside the nacelle, such as bearings, may need to be maintained timely, if do so, the nacelle and blades connected together need to be disassembled first from the top of the tower, and then hanged down on the ground or on the deck for replacement. As result it will be a hard task which not only costs money but takes time, and probably even gets worse when the weather is bad.
Besides the wind turbine, it likely needs to provide a possible solution to replace worn component, such as bearings, of any other machine that would not be allowed to be disassembled or to be moved on site.